a) Field of the Invention
The present invention relates to a building, and more particularly to a natural convection roof device which can be installed on the roof of a greenhouse, heat pipe, warehouse, animal house or transportable building used in agriculture, industry and business, in addition to the roof on an ordinary fixed building. The natural convection roof device ventilates and stops rain, and some roof devices can protect with multi-layers. Hot air in a building flows upward to an inner ventilation opening from bottom to top, through center ventilation openings and is then discharged from ventilation holes without being affected by the potential drop, so that there is no need to press down the hot air. An inner barrier is used to provide the function for stopping the counter flow rain and to allow the rain to blast the rain which flows upward against the stream from drain holes by free falling upon entering into the building from the ventilation holes, so that the rain can be discharged successfully from the drain holes. Furthermore, the hot air in the building is discharged out of the building, whereas cold air is drawn in by natural convection.
b) Description of the Prior Art
A conventional building absorbs heat easily and does not dissipate heat easily when being exposed to sunlight. In particular, a concrete building absorbs heat easily and does not dissipate heat easily once being exposed to sunlight for a long time in a daytime, which increases the indoor temperature. Furthermore, as hot air ascends from bottom to top, the indoor temperature will be increased continuously. Therefore, during the summer, the interior of the building is still very hot even in the night.
There are several cooling methods used often nowadays. However, their effects are inferior. Some vendors will install a fixed sprinkler on the roof, which requires additional hoses and water loops. Besides that, a water switch needs to be turned on manually or an automatic water switch has to be installed. This wastes water resources, and the area of sprinkling is incomplete and non-uniform to limit the cooling effect. Other vendors will install a cooling fan on the roof to discharge hot air by forced convection of rotation. However, the cost of the cooling fan is high and the roof needs to be cut when implementing the cooling fan. Therefore, the cooling effect is still limited.
Some vendors will change the building materials. However, the heat-proofed or heat-isolated building materials are expensive.
It can be seen that there is a small rooftop on the apex of a ridge on a conventional building. Two sides of that small rooftop ventilate and can be installed with a window, blind or net to discharge hot air in the building through the two sides of the small rooftop. However, when it is raining or a hurricane comes, the rain with strong wind can also permeate into the building through the window, which is not helpful.
On the other hand, a small eave (or attic) can be installed on a side of a pitched roof. The small eave is also provided with a window, blind or net to discharge hot air in the building through the window, which also results in the abovementioned shortcoming that when it is raining or a hurricane comes, the rain with strong wind can permeate into the building through the window too, which is not helpful.
The two rooftop cooling methods described above are all based on the principle of air convection to dissipate hot air in the building. It means that when hot air in the building ascends, hot air can be dissipated out through windows on a little rooftop (eave). Although there is no need to use power to dissipate heat effectively, rain along with strong wind may also penetrate into the building through the windows, resulting in counter flow wind and dripping rain, which is the most disturbing thing.
FIG. 1 shows a cutaway view of a first prior art, the U.S. Pat. No. 6,966,156. An interior of a roof 20 is provided with a ventilating duct 21, two sides of the ventilating duct 21 are provided respectively with a weather-blocking panel 22, above the weather-blocking panels 22 are plural vents 23, and below the weather-blocking panels 22 are exhaust orifices 24. In addition, an interior of each weather-blocking panel 22 is provided with a valve switch 25. When hot air in the building rises up along the ventilating duct 21 and flows into the weather blocking panels 22 through the vents 23, the valve switch 25 are opened to dissipate hot air from the exhaust orifices 24.
To shield from rain, the roof 20 in the abovementioned invention is sealed and hot air is concentrated in the ventilating duct 21 based upon the principle of hot air rising. However, as the exhaust orifices 24 are lower than the outlet of the ventilating duct 21 by a potential drop h1, the force of heat flow in the ventilating duct 21 must be much larger than the potential drop h1 of the exhaust orifices 24 that heat can be dissipated out by the power of the rising hot air. Besides that, as the exhaust orifices 24 for dissipating heat is faced downward, hot air is often concentrated in the ventilation duct 21 and cannot be dissipated successfully. Although the roof 20 can shield from counter flow rain, the effect of heat dissipation is not perfect.
FIG. 2 shows a cutaway view of a second prior art, the U.S. Pat. No. 5,052,286. A lower part at two sides of a roof 30 is provided with plural ventilation holes 31, and the lowest parts at two sides of the roof 30 are also provided with drain holes 32. To shield from rain, the roof 30 is sealed and hot air is concentrated above the roof 30 based upon the principle of hot air rising. The ventilation holes 31 and the drain holes 32 are lower than the region where heat is concentrated; therefore, the force of heat flow at the heat-concentrated region must be much larger than the potential drops h2, h3 of the ventilation holes 31 and the drain holes 32 that heat can be dissipated out by the power of hot air rising. In addition, as the ventilation holes 31 and the drain holes 32 for dissipating heat are faced downward, hot air is often concentrated in the heat-concentrated region and the effect of heat dissipation is not perfect.
Accordingly, to solve the abovementioned shortcomings, the present inventor has already filed the application of invention patent No. 09813370, “Ventilation and Rain Stopping Device without using Power,” to the Intellectual Property Office of Taiwan and has been issued with the patent No. I374212 (the present inventor also has applied for the U.S. patent Ser. No. 12/590,223, “Ventilated Roofing Structure,” and has been issued with the U.S. Pat. No. 8,322,088).
FIG. 3 shows a cutaway view of a third prior art, wherein a roof 10 on a building includes a first roof drainage panel 11, second roof drainage panels 12 and inner barriers 13. The first roof drainage panel 11 is an upper roof with multiple layers, and there are two second roof drainage panels 12 disposed at a left and right side of the first roof drainage panel 11. The first roof drainage panel 11 is a cone-shaped rooftop which is extended downward by a certain distance to a center ventilation opening 14. The space between the center ventilation opening 14 and the cone-shaped rooftop is covered by the first roof drainage panel 11. The first roof drainage panel 11 is provided with a tail end B1 which is in adjacent to the center ventilation opening 14. The second roof drainage panels 12 are connected above the tail end B1 of the first roof drainage panel 11 and are disposed outside the first roof drainage panel 11. In this embodiment, the second roof drainage panels 12 are vertical, which keeps an outer ventilation opening 15 between the top ends A1 of the second roof drainage panels 12 and the first roof drainage panel 11. The inner barriers 13 are formed by extending the roof 10 upward and are connected below the tail end B1 of the first roof drainage panel 11; whereas, there are inner ventilation openings 16 between the inner barriers 13 and the first roof drainage panel 11. In this invention, the relationship among the first roof drainage panel 11, the second roof drainage panels 12 and the inner barriers 13 are that the top ends A1 of the second roof drainage panels 12 are higher than the tail end B1 of the first roof drainage panel 11, and the tail end B1 of the first roof drainage panel 11 is disposed between the top ends A1 of the second roof drainage panels 12 and the inner barriers 13.